Apparatus for polishing sheet material



Jan. 12, 1965 C. A. HESS ETAL APPARATUS FOR POLISHING SHEET MATERIAL Filed Sept. 10, 1962 ATTORNEYS United States Patent "cc APPARATUS F91 1 PULHSHHNG SHEET MATERIAL Charles A. Hess, Perryshnrg, and .lohn M. Byal and Milton Adams, Toledo, @hio, assignors to Libbey- Gwens-Ford Glass Company, Toledo, Ohio, 2 corporation of Ghio Filed Sept. 10, 1962, Ser. No. 222,517 6 Claims. (Cl. -23019) This invention relates generally to the surfacing of sheet material and, more particularly, relates to an improved polishing apparatus or runner for use in the production of polished strip or ribbon material such as ground or polished plate glass.

In the production of plate glass, a continuous ribbon of predetermined width and thickness is normally formed from a mass of molten glass, which ribbon is annealed and thereafter conveyed through a grinding and polishing line. is conveyed in continuous form and ground and polished upon both sides simultaneously or, in accordance with another known technique, the ribbon is cut into sheets which are then bedded in plaster on suitable tables and ground and polished first on one side and then on the other.

Generally, the sheets or ribbon are polished by means of substantially circular polishing runners or blocks, a plurality of which are joined together to rotate as a unit about an axis perpendicular to the glass surface, while each individual runner is itself mounted for rotation about its own axis. The generally flat, rigid surfaces of these polishing runners or discs which define the working faces thereof and are pressed into polishing engagement with the sheet include a polishing pad normally composed of a fibrous material such as felt. It is conventional practice to cut the felt pads to a diameter somewhat greater than the diameter of the runner and to then secure the felt disc to the runner by drawing the marginal edge of the pad around the outer circumference of the runner, such marginal edge then being clamped about the periphery by a metallic ring.

With the use of the prior art apparatus as above described, some difiiculty has been encountered in uniformly polishing the glass surfaces due to such surfaces not always lying entirely in true plane. For example, minute grooves or valleys are sometimes found to exist in the surfaces of the sheets whereby the lowermost portions of the valleys or grooves are often not contacted and acted upon by the generally tightly stretched, taut felts. Failure of the felts to contact and polish these valleys of course results in an imperfect and commercially unacceptable sheet.

It has now been discovered, and the instant invention vis based upon such discovery, that the positioning of a plurality of "resilient spacer members or pads between the rigid working face of the runner and the felt, which pads are spaced relative to one another across the working face, tends to give to the felts a somewhat flexible nature thereby enabling them to assume substantially the precise shape of the corresponding surface being polished and accordingly effect a more uniform polishing of the sheets.

It is. therefore a principal object of the invention to provide an improved polishing apparatus or runner for use in the production of sheetmaterial such as ground and polished plate glass.

A further object of the invention is the provision of an inexpensive and relatively simple innovation for polishing runners which may be quickly and easily incorporated into apparatus of conventional design as now commonly employed in the. glass industry.

According to one known practice, the ribbon 3,lhd,854 Patented Jan. 12, 1965 Other objects and advantages of the invention will become more apparent during the course of the following description when taken in connection with the accompanying drawings.

In the drawings, wherein like numerals are employed to designate like parts throughout the same:

FIG. 1 is a schematic, plan view of a series of polishing stations each including a plurality of runners constructed in accordance with the present invention;

FIG. 2 is a vertical cross sectional View of the improved runner in accordance with the invention;

FIG. 3 is a plan view illustrating the position of the resilient spacer members or pads relative to the runner working face, shown in phantom, and the polishing pad, according to one embodiment of the invention; and

FIG. 4 is an enlarged, fragmentary, vertical sectional view through the working face of a polishing runner in accordance with the invention and illustrating the improved action thereof when the runner is pressed into polishing engagement with a glass sheet having a somewhat uneven surface.

Generally stated, the present invention provides an apparatus for polishing sheet material such as glass and the like including a polishing runner having a rigid, generally fiat portion defining the working face thereof, a polishing pad secured about the periphery of said ruuner'and substantially completely covering said working face portion, and a plurality of resilient spacer inserts disposed between said rigid working face of the runner and said pad in spaced relation to each other. In this respect, while the invention will hereinafter be described specifically in connection with the polishing of glass and the use of runners or polishing tools having a particular configuration, grouping and/or motion, such description is in no way intended to be limitative. Thus, essentially any known or conventional surfacing apparatus may be modified in accordance with the invention, and various other substantially flat, hard sheet materials in addition to glass surfaced therewith, without loss of the important advantages obtained by an appreciation of the basic concepts of the invention.

Referring now more particularly to the drawings, there is illustrated schematically in FIG. 1 a plurality of polishing stations 10 which make up a portion of a grinding and polishing line. Glass sheets 11 which may be suitably bedded upon a number of tables 12 in a layer of plaster of Paris or the'like 13 are continuously moved in the direction of the arrow 14 to carry the sheets to each station. In this respect, each station 10, in the particular embodiment illustrated, includes six circular runners or polishing blocks 15 arranged in pairs and driven to rotate as three units in the direction of the arrows 16 about vertical axes passing through the midpoints of connecting beams 17 joining the two runners of each pair together, which axes are disposed perpendicularly to the major surfaces of the glass sheets 11. The pairs of runners are mounted such that their rotational paths of travel overlap whereby every point on the upper surfaces of the glass sheets passing therebeneath is contacted by the working face of at least one runner. In addition, each individual runner 15 is also mounted for rotation about its own axis, such as indicated at 18, to impose an additional polishing action on the sheet surfaces.

As most clearly shown in FIG. 2 of the drawings, each runner 15 comprises a hollow metallic pan-like member 19 having a fiat, broad, substantially rigid surface 20 which forms the working face thereof. Located at three points spaced equally about the runner adjacent the periphery thereof are bearing wells 21 which receive shafts (not shown) extending from a conventional spidertype runner drive mechanism. The bearing wells 21 may suitably include slots 22 in the side walls thereof in which tongues affixed to and projecting from the shafts are received in order to allow a slight amount of relative horizontal movement or play between such shafts and the runners during rotation thereof.

A polishing pad 23 composed of felt or the like fiibrous material and of generally square outline is secured to the pan-like member 19 at the upstanding peripheral wall portion 24 thereof by means of an expandable metallic retaining ring 25. In this respect, the length of each side of the square pad 23 is preferably substantially equal to the diameter of the runner pan 19 whereby four corner portions 26 are provided which extend beyond the periphery of the runner and are held by the ring 25 in engagement with the wall 24 when the felt is drawn tautly across the working face of the runner.

The structure of the runners 15 as above described may be considered for the most part to be conventional and capable of employment without further modification in a present-day polishing line. However, and as previously mentioned, it has been found to be extremely diflicult when employing runners of this general structure to uniformly polish glass sheets having grooves or small valleys in their surfaces not completely removed by the grinding operation or due to handling between the grinding and polishing operations. Thus, with a uniform polishing pressure being applied over the working faces of the runners, the taut felt pads were not able to conform sufiiciently to the sheet surfaces to accomplish an even polishing action.

In accordance with the present invention, a plurality of pads or spacer inserts 27 composed of a resilient material are disposed between the rigid pan bottom 20 of the runner and the polishing felt in spaced relation across the working face, which inserts are effective to impart a highly flexible nature to the polishing felt and enable same to assume substantially the precise configuration of the glass sheet surface while a uniform polishing pressure is still, for all intents and purposes, exerted on every point on such surface. While the exact number, position and dimension of the spacer pads are to some extent a matter of choice, it has been found to be advantageous to position the resilient inserts 27 about the periphery r perimeter of the polishing runner working face thus leaving at least the central portions of the felt polishing pad 23 spaced somewhat from the pan bottom 20 and free of a resilient backing. In this respect, excellent results have been obtained when using four substantially square pads positioned relative to each other as best illustrated in FIG. 3. The spacer pads 27 may be suitably retained in their illustrated position by disposing the sides or edges thereof substantially parallel to the edges of the felt 23, with corner portions 28 extending beyond the periphery of the runner or pan 19 such that these portions will be folded during installation together with the corner portions 27 of the polishing pad itself and also retained by the metallic ring 25.

While the spacer pads or inserts 27 may be composed of substantially any resilient, relatively soft material, good results to date have been obtained with the use of both polyurethane foam and sponge rubber. The inserts only need be of relatively small thickness, for example, from about .30 to .75 inch thick in order to successfully enable the desired deviation of the felt. In this connection, good results have been obtained when the inserts had a rebound hardness of approximately five Shore durometer. The average useful life of such inserts, i.e. composed of either polyurethane foam or sponge rubher, has been found to be of substantial length before failure thereof, usually caused by loss of the necessary resiliency or elasticity, is observed.

As a specific example of a runner constructed in accordance with the invention, and particularly of the relative sizes of the spacer inserts and felt, four sponge rubber inserts approximately 7.5 to 8 inches square and .375 inch in thickness have been employed and positioned approximately 2 inches in from the corners of a felt pad 25 inches square and 1.25 inches thick. The upstanding pan wall 24 in this embodiment was approximately 2.25 inches high and .25 inch thick.

In addition to the use of the square insert or spacer members, triangular shaped pads have also been employed successfully, such triangular pads being positioned similarly to the square inserts 2'7 with one vertex thereof disposed outwardly of the periphery of the pan and folded and secured with the corners of the polishing felt. Further, while excellent results have been obtained with the use of four spacer pads, satisfactory results may also be obtained with three or even two pads spaced across the working faces of the runners.

Turning now to FIG. 4, there is illustrated the improved action of the novel polishing runner in accordance with the invention during the polishing of a glass sheet having a somewhat irregular surface. Thus, a portion of the polishing pad or felt 23, because of the resilient, spaced inserts 27, is permitted to deviate slightly from the plane of the rigid working surface of the runner into surfacing engagement with the lowermost portion of a groove 29 located in the surface of the glass sheet 11 without disturbing or disrupting the substantially uniform polishing pressure applied across such working face of the runner. This action is due to the use of the plurality of inserts which are of relatively small area with regard to the area of the felt polishing pad itself, and their spacing across the working face of the runner.

It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred embodiment of the same, and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention.

We claim:

1. In apparatus for polishing sheet material such as glass and the like, a polishing runner including a hollow pan-like member having a rigid, substantially fiat portion which defines the working face of the runner and a side wall portion surrounding and extending upwardly from said flat portion, a polishing pad secured to the runner about said side wall and completely covering said working face portion thereof, and a plurality of resilient inserts disposed between said rigid flat portion of the runner and said polishing pad in spaced relation to each other, said inserts being positioned adjacent the perimeter of said flat portion and dimensioned inwardly thereof so as to leave the centrally disposed area of said polishing pad spaced from said flat portion and completely free of resilient backing, with a portion of said inserts extending beyond said flat portion and also being secured adjacent said side wall.

2. In apparatus for polishing sheet material such as glass and the like, a generally circular polishing runner including a hollow pan-like member having a rigid, substantially fiat portion which defines the working face of the runner and a cylindrical side wall portion surrounding and extending upwardly from said flat portion, a polishing pad secured to the runner about said cylindrical side wall and completely covering said working face portion thereof, and a plurality of resilient inserts disposed between said rigid flat portion of the runner and said polishing pad in spaced relation to each other, said inserts being positioned adjacent the perimeter of said fiat portion and dimensioned radially inwardly thereof so as to leave the centrally disposed area of said polishing pad spaced from said flat portion and completely free of resilient backing, with a portion of said inserts extending beyond said flat portion and also being secured adjacent said cylindrical side wall.

3. Apparatus in accordance with claim 2, wherein said resilient inserts are composed of sponge rubber.

resilient inserts have a Shore durometer rebound hardness of approximately 5. a

6. Apparatusin accordance with claim 2, wherein said ness,

resilient pads are approximately .30 to .75 inch inithick- References Cited in the tile of this patent UNITED STATES PATENTS Kent et a1 -1 Mar. 9, 1920 Singley Oct. 4, 1955 Hoyet et a1 -1 Aug. 29, 1961 

1. IN APPARATUS FOR POLISHING SHEET MATERIAL SUCH AS GLASS AND THE LIKE, A POLISHING RUNNER INCLUDING A HOLLOW PAN-LIKE MEMBER HAVING A RIGID, SUBSTANTIALLY FLAT PORTION WHICH DEFINES THE WORKING FACE OF THE RUNNER AND A SIDE WALL PORTION SURROUNDING AND EXTENDING UPWARDLY FROM SAID FLAT PORTION, A POLISHING PAD SECURED TO THE RUNNER ABOUT SAID SIDE WALL AND COMPLETELY COVERING SAID WORKING FACE PORTION THEREOF, AND A PLURALITY OF RESILIENT INSERTS DISPOSED BETWEEN SAID RIGID FLAT PORTION OF THE RUNNER AND SAID POLISHING PAD IN SPACED RELATION TO EACH OTHER, AND INSERTS BEING POSITIONED ADJACENT THE PERIMETER OF SAID FLAT PORTION AND DIMENSIONED INWARDLY THEREOF SO AS TO LEAVE THE CENTRALLY DISPOSED AREA OF SAID POLISHING PAD SPACED FROM SAID FLAT PORTION AND COMPLETELY FREE OF RESILIENT BACKING, WITH A PORTION OF SAID INSERTS EXTENDING BEYOND SAID FLAT PORTION AND ALSO BEING SECURED ADJACENT SAID SIDE WALL. 